Party-line telephone system



Jan. 16, 1923.

T. G. MARTIN.

PARTY LINE TELEPHONE SYSTEM.

FILED JULY 20,1905.

ififfiwgsf 'YDJK/ wall 1 Jan. 16, 1923. I 1,442,082.

T. G. MARTIN.

PARTY LINE TELEPHONE SYSTEM.

FILED JULY 20, 1905. 6 SHEETS-SHEET 2.

GSHEEYS SHEET 3.

Jan. 16, 1923.

T. G. MARTlN.

PARTY LINE TELEPHONE SYSTEM.

FILED JULY 20,1905- 6 SHEETS SHEET 4.

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T. G MARTIN. PARTY LINE TELEPHONE SYSTEM.

FILED JULY 20,1905.

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a SHEETS-SHEET s T. e. MARTIN. I PARTY LINE TELEPHONE SYSTEM.

FILED JULY 20, 1905.

Jan. 16, 1923.

\wh wmm mm r mwmxwm w Nhw Patented Jan. 16, 1923.

UNITED STATES I 1,442,082 PATENT OFFICE.

TALBOT G. MARTIN, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

AUTOMATIC ELECTRIC COMPANY, A CORPORATION OF ILLINOIS.

PARTY-LINE TELEPHONE SYSTEM.

Application filed July 20, 1905. Serial No. 270,591.

Illinois, have invented a certain new and useful Improvement in Party-Line Telephone Systems, of which the following is a specification. v

My invention relates to automatic telephone exchange systems in general, but more particularly to those systems in which the central station or exchan e apparatus comprises a suitable number of electricallypropelled and step-by-step-aotuated switchmg machines, and especially to automatic telephone systems of this type in which the current employed by the subscribers for operating the switching apparatus at the central station or exchange is supplied from a battery or other source which 18 common to all of the different subscribers lines in the system, or at least to. a certain number of such lines, according to the conditions and requirements of different cases. In the type of automatic telephone exchange system to which my invention more particularly relates, each subscriber is provided with switching means termed a calling devicethat is, a device by which he calls the number of any other subscriber; andit will be understood, of course, that each subscribers equipment comprises also a transmitter, a receiver and hook-switch, together with a hell or other suitable call-signal. In systems of this character, each subscribers line terminates in more or less apparatus which is individual to the line-that is to say, each subscribe'rs line runs from a subscribers station to some point'at or near the central station or exchange, or to some other outlying point, and there terminates in apparatus having certain parts or devices which are individual to that line, and which are used by the subscriber of that line and no other. For example, each subscribers line may terminate in an electrically-propelled and step-by-step-actuated switching machine of the type known as a first-selector, each first-selector being individual to its allotted subscribers line, and constituting a piece of switching apparatus which is used by that subscriber and no other. In addition, in a system of this character, there-may be other slmilar switching machines known as second or third or even fourth selectors, each of which is more or less common to the different subscribers, or to a certain proportion of the entire number of subscribers. Also, in an exchange comprising switching apparatus whereby one subscriber may connect his line withthe line of another subscriber, without the assistance of an operator at the central station there is preferably another class of electrically-propelled and step-bystep-actuated switching machines of that type known as connectors.

The selectors are each employed for automatically selecting an idle trunk-line leading to the desired group of switching machines, either selectors or connectors, according to the size and capacity of the exchange; but a connector is adapted and employed for making the finalconnection directly with the line of the called sub scriber. Consequently, any calling subscriber may operate his calling device, so as to call the-number of the called subscriber, and thereby produce such operations on the part of certain of the switching machines in the exchange aswill connect his line with the called subscribers line, providing, of course, that the called subscriber is not already using hislline, or that some other subscriber has not already connected his line with that of the called subscriber. The calling of any desired number consists, it will be understood, in simply producing a makean-d-break action in a grounded line-circuit including one side of the calling subscribers line, and in another grounded circuit including the other side of the calling subscribers line. For example, if the calling subscriber desires to connect his line with that of another subscriber whose number is 410, the operation of calling the desired number is as follows: The calling subscriber momentarily closes one of the ground-circuits four-times in succession, so as to produce four distinct and successive electrical impulses in the said circuit; and preferably, and in a system of the character to which my invention more particularly relates", he then follows these four electrical impulses with a, single impulse in a ground-circuit including the other side of his line, so as to not only cause his first-selector to pick out the debe in an idle or non-busy condition. In other words, the calling'subscribers firstselector responds to the four impulses and proceeds, under the direct control of the calling subscriber, to pick out the desired group of trunk-lines; but at this point in its operation the said first-selector escapes, so to speak, from the control of the calling subscriberand proceeds automatically and by itself to pick out and establish connection with the first trunk-line in the group which is found to be idle and in condition to be appropriated by the calling subscriber as a means of establishing connection between his line and that of the called subscriber. This means accomplished in the switching operation by which the calling subscriber, by his own acts and without the assistance of an operator, connects his line with the line of the called subscriber, the said calling subscriber then operates his calling device in such manner as to first transmit a single impulse over one side of the line,. this opera tion corresponding, it will be observed, to the second digit of the called subscribers number; and this is followed, of course, by

the single impulse over the other side of the line. This single impulse transmitted over the so-called vertical side of the line-circuit is received by or transmitted through the apparatus of a connector situated at the end of the trunk-line which was automatically selected by the first-selector. Accordingly, the said connector responds by picking out the group of subscribers lines in which the called subscribers line is included;

but it will be seen that the connector mustnow complete the work for which it has been appropriated by the calling subscriberthat is, must find the exact subscribers line with which the calling subscriber desires. connection. Now it will be seen that in the case of a selector, the first part of the operation thereof was under the direct control of the calling subscriber, while the remainder of the operation, which consisted in making connection with the trunk-line, was accom; plished automatically by the selector and without the aid of the calling subscriber. \Vith the connector, however, the situation is quite different; for the establishment of connection between the two subscribers lines has now arrived at a point where it is simply a matter of making connection with a certain subscribers line and no other, as the calling subscriber, of course, desires to establish connection with this particular subscribers line. While the calling subscriber was extending the connection from his line to a connector, it mattered little to him how that connection was made,or over which of the many trunk-lines that connection was accomplished; for with quite a number of trunk-lines extending between the different groups of switches, the calling subscriber is not concerned'with the manner in which his line is finally connected with a connector that is to say, any one of a certain number of trunk-lines may be used, and any arrange ment will serve his purposes so long as a connection is finally established with one of a certain number of connectors each of which is capable of establishing connection directly with the line of the called subscriber. It is for this reason, therefore, that the entire operation ofa connector, in establishing the desired connection, is under the direct control of the calling subscriber, so that he may not only cause the connector to pick out the particular group in which the calledsubscribers line is included, but may also then cause the connector to pick out and establish connection with the particular or desire-d line in such group. Consequently, the calling subscriber now completes the operation of the connector by so operating his calling device as to transmit ten successive electrical impulses over one side of the line-circuit, this operation corresponding to the cipher or last digit of the called number; and theseten electrical impulses transmitted over a grounded linecircuit including one side of the line are then followed immediately by the single impulse transmitted over the other side of the line, as will hereinafter more fully appear. This final operation completes the connection between the calling and the called subscribers lines, and the calling subscriber may then press his so-called ringing-button and thereby cause a relay in theconnectorto temi porarily connect the so-called ringing-generator with the line of the called subscriber, thus ringing the bell at the called subscribers station. In this example of the use of a subscriber-operated exchange apparatus for automatically establishing connection between subscribers lines, it will be observed that the system involves only a comparatively small number of subscribers, thereby rendering the employment of intermediate selectors unnecessary; for unless the calling subscriber desires to call a subscriber true of any subscribers line which is in use,

as it is obviously desirable that a calling subscribers line be protected against seizure during the time he is endeavo'ring to communicate with the called subscriber, and

- of other subscribers.

that a calling subscribers line be protected against seizure by a third subscriber before the called subscriber answers; and while the two subscribers are conversing, the two lines and the trunk-line connection by which they are connected, and -in fact the entire talkingcircuit thus temporarily established between the two subscribers, must be made immune against seizure by other subscribers as well asagainst listening-in on the part Again, the construction and arrangement is preferably such that a calling subscriber can release any and all of the switches which he may have put in operation, either before or after the calling subscriber answers, and it is also desirable that the called subscriber be able to at least restore the connector and thereby disconnect his line from that of the calling subscriber; and it is even the practice generally to so construct the apparatus that either the calling or the called subscriber may eifect a complete and total release and restoration of all switching machines which may have been employed in establishing connection between their two lines. The current for talking purposes may be furnished either by local batteries at the subscribers stations, or by acentralized source of supply; but the current for operating the switching machines is preferably furnished from the battery or other centralized source of supply, and the current for ringing the bells at the subscribers stations is also preferably derived from suitable generating means at the exchange or central station.

Generally stated, the object of my invention is the provision of an improved construction and arrangement whereby an automatic telephone system of thefforegoing character, or of substantially the foregoing character, may be operated on the partyline basis, so that one or more of the subscribers lines therein may be provided with a plurality of subscribers stations, and whereby any subscriber may establish connection with any such party-line and signal the desired subscriber on that line, or whereby any subscriber on a party-line may signal and communicate with another subscriber on the same line. Special objects of my invention are to provide an improved construction and arrangement for selectively signaling the difi'erent'subscribers on a party-line in an automatic telephone exchange system of the foregoing character; to provide an improved construction and arrangement whereby, in an automatic telephone exchange system, the difi'erent subscribers on a party-line may each have a difierent number, and whereby any calling subscriber may call any one of these numbers and obtain connection with such partyline, but whereby the bell at the called subscribers station will always ring to the exclusion of 'all other bells on the same line; to provide an improved construction and arrangement whereby several subscribers on the same line maybe selectively called or signaled through the medium of a plurality of groups of connectors, said groups corresponding in number to the number of subscribers on the line, and whereby the employment of any connector in any group by a calling subscriber will accomplish the same result, as far as connective urposes are concerned-that is, will estabiish connection with, the party-linebut whereby the use of any connector will inevitably result in the transmission onto the partyline of a ringing current of such character that only one bell will ring, namely the one at the sub-station which corresponds to the connector in use, or which corresponds, more properly speaking, to the group of connectors in which is included the particular connector by which the calling subscriber establishes connection with the party-line; to provide an improved construction and arrangement by which connection may be established with a partyline through the medium of a plurality of groups of connectors, there being as many groups as there are subscribers stations on the party-line, and the contacts or line-terminals which are allotted to one subscribers Station, and which are multipled together horizontally in a certain level of a certain group of connectors, being cross-multipled vertically with the groups of contacts or line-terminals which are allotted to the other stations on the same line, and which are located in corresponding levels in the other groups of connectors, the contacts or line-terminals representing one subscribers station being located, for example, in the first level of the banks of a certain group of connectors, those belonging to another subscriber being located in the same level of the banks of another group of connectors, and so on, each subscribers station being given a set of multiple-contacts or line-terminals which are located in the first level of the particular hundred-group of connectors to which the subscriber belongs, and each of the difi'erent groups of connectors which are allotted to the different hundred-groups to which the different subscribers of the party-line belong being equipped for transmitting a difierent' kind of ringing current, whereby any connector in any of the said groups is operative to establish connection with the said party-line, but whereby whenever a connection is thus established only that bell will ring which belongs to the called subscriber-that is, the subscriber whose station corresponds to the particular group of connectors in which is included the connector which was automatically connected with the calling submomentarily remove the guarding potential established through the rivate-bank-con. tacts of his first-selector when he mo-' mentarily grounds the so-called' rotary V side of his line-as, for example, in com-' connector. for-calling and signaling another subscriber on the same line, it being.

pleting the operation of a connector for the purpose of closing connection with the line-selected by 'the connector whereby a party-line subscriber may employ the proper observed that-in such case the calling subscriber must, so to speak, call his own line and thereby compel the connector to make connection with a line whichis busy, and which is in condition to ordinarily defeat any attempt on the .part of a connector to establish a connection therewith; and to provide certain details of construction andfeatures of improvement and combinations tending to increase the general efliciency andserviceability of an automatic party-line telephone exchange system of this particular character, and to advance the art of telephony generally.

To the foregoing and other useful ends, my invention consists in matters hereinafter set forth and claimed.

A brief description of the accompanying drawings is as follows:

Figures 1, 2 and 3, taken together, represent in diagram the circuits and mechanical details involved when one subscriber has called another. The sub-station A in Fig. 1

(No. 500) is shown as having called substation No. 10 in Fig. 3. At B (Fig- 1) there is represented the first-selector of the calling subscriber in its connective position in the circuit. In Fig. 2, (1 indicates the position of the connector which has completed the circuit, and which is a member of a group ofconnectors that use ourrent for ringing purposes from a suitable generator D. Another connector of another group is" indicated at E and this, latter connector uses current from anotherv generator F. The connector of another group. is shown at G which uses current for ringing purposes from the group generator H., And still another connector is shown at 1 with its particular group ringing generator J. Y I

Fig. 3 is a diagrammatic 'drawingof a party telphone line to which there are connected four. sub-stations, their numbers being 110, 210, 310 and 410, designated. These stations have afirst-selector K in 1,44a,osa

common, and may call each other selectively. Also a party of another line may be called by them individually, or he may callany of them selectively. These operations will be fully described hereinafter.

Fig. 4 is a diagrammatic perspective view of the first-selector B, showing the circuits and operative parts of the mechanism, omitting the switch-frame. Underneath the switch the private and the line banks are shown, the former above the latter.

Fig. 5 is a diagrammatic perspective drawing of the connector 0 Fig. 6- represents the sub-stations 110, 210, 310 and Y410 of Fig. 3, where one of said substations (No. 110) hascalled another subscriber (No. 410) on his own line.

The construction and general operation. of the 'difierent devices and switching I118. chines are asfollows: I

The first-selector K, which is the same as first-selector K of Fig. 3, is shown 0perated and connected with the connector C, which latter is the same asconnector (3 of Figs. 2 and 5. Connector-groups,

such as the vones represented in Fig. 2, may.

correspond in number to the maximum numher of subscribers which the exchange can maintain on a single line. This arrangement is necessary in order that access may be had to adiiferent ringing generator for signaling a difierent subscriber on each party line. The hell or ringing apparatus at each telephone is so adjusted that only alternating current of a particular frequency will afitect each one of them; and the frequency that will aflect one of the substations on the line will not affect any of the others on the same line. Therefore, if there are four parties on one line, to signal each one there is required current of four different frequencies; and there are required, therefore,'the services of four different generators, and consequently four different connector-groups must have access to the line to which the four parties are connected. This arrangement is clearly indicated in Fi 2 and 3. The connectors C", E, G and 1 belong respectively to the so-called 400, 300, 200 and- 100 groups. It will 'be seen that the connector C is connected to the tenth terminal of the fourth level of the line-bank of the first-selector .B (Fig. 4), and that connectors E, C and I 'are connected, respectively, to. the

connect in multiple all corresponding tenth 12f) tenth contact of the third, second and first levels. In Fig. 2 the conductors 2, 3 and 4' bank-contact-points of the 400-connectorbanks, similar to the banksshown in F ig. 4. Opposite each set ofthese is a connector parallel with connector C. These latter, in regular order, are con- 1 banks there v nected by trunk-lines to corresponding contacts of the fourth level of the first-selector-- banks parallel with the trunk-lines of connector C". The trunk-line leading from the first contacts of the fourth row or level of the first-selector B. for instance, would terminate in connector C the position of which connector is opposite the bank-conhundreds by conductors, as is indicated by the lines 5, 6 and'7. A similar construction is true of all other corresponding contactpoints. If there should be only three parties one line, it is evident that it would be necessary to cross-multiple only three of the hundreds, such, for-instance, as the fourhundred group, the three-hundred group and the two-hundred group.

Any subscriber desiring connectlon with the party-line subscriber No. 410 must use ,the ringing current generator of the four-hundred group. The calling firstselector therefore, is raised to the fourth level. and an idle connector of that group is selected. It has been'explained that all the connectors of the fourhundred group terminate in the fourth level of the firstselec-tor-banks, and that they draw their ringing current from ringing generator Then if the connector C is selected, it is raised to the first level and rotated ten steps, placing the calling line in connection with the trunk-conductors 6 and 7 and,-

therefore, with sub-station No. 410 (Fig. 3). As the bell of only this sub-station is adjusted to respond to the current of ringing enerator D, only said bell will respond to t he ringing current therefrom. If party No.

, 310 is desired instead, the first-selectorwipers are then raised to the third level of the bank-contacts and cut-in onto some connector of the three-hundred of E groupthat is, these selector-wipers are caused to stop on contacts connected with tery, the positive terminal of which preferably is grounded. All of the sub-stations are constructed the same, with the exception of the ringers or bells, and in Figs.- 1, 3 and 6 like parts are represented similar- 1y. Each sub-station, Fig. 1. for instance,

hook 9, ringer 10, transmitter 11, induction coil 12, local battery 13, and a condenser 14. The induction-coil, of course, is made up of a: primary and a secondary winding 15 and 16, respectively. The switch-hook is designed to control the local-circuit-springs 17 and 18, the secondary-circuit-springs 19 and 20, and the ground-circuit-springs 21 and 22. In addition, the subscribers telephone apparatus is furnished with a signaling-button 23 which may be ressed against the spring 24 that is normally closed with contact-point 25. When said button is pressed, the spring 24 breaks with contact-point 25 is provided with the usual receiver 8, switchand closes with contact-point 26. The calling device at each telephone may be of any well-known or suitable type, and issimply represented in Fig. 1 by two push-buttons 27 and 28, two springs 29 and 30 and three contact-points 31, 32 and 33. The first-selector of my invention may be of any well- 7 known or suitable type,'-such, for instance, as the first-selector B represented in connection with sub-station A, Fig. 1. The mechanism and circuits of this selector are clearly shown in Fig. 4. The line-conductors 34 and 35 of sub-station A terminateat this switch in-certain relays. The vertical-line-conductor 34 is connected with the relay 40, which is known as the vertical-line-relay, and the rotary-line-conductor 35 terminates in the second relay 41, known as the rotary-line-relay Through their armaturesthe verticalrelay-armature 42 and the rotary-relayarmature 43these relays have supervision over the so-called line-relay-springs 44, 45 and 46, and over certain internal circuits which are hereinafter described. For example, one of these circuits includes an electro-magnet known as the vertical-magnet 47 which consists of two coils 48 and 49. These coils and their cores, when energized, operate an armature 50 which is sup-- ported from the switch-frame by two pivots 51 and- 52. Said armature is normally held away from the vertical-magnet-polepieces by a retracting-spring 53. When this armature is actuated, it operates certain devices through the medium of an arm 54, which latter constitutes part of said armature and is known as the vertical-arm This arm has on its lower side an L-shaped piece 55, and on its forward end a pawl known as a vertical-pawl 56, which latter is pivotally secured to said end. This pawl is held in position b a small retracting-spring 57, one end 0 which spring is attached to the rear end'of the verticalpawl, and the other to the body of the vertical-arm 54. A second electro-mag-' net, indirectly controlled through the linerelaysprings is the rotary-ma et 60. This rotary-magnet is provi ed with two coils or windings 61 and 62, and

operates certain mechanism through an armature known as the rotary-armature 63, said armature being supported from the switch-frame ina vertical plane, by two ivots 64 and 65. --.'This armature performs 1tS Work while moving in an oscillatory manner under the. influence of the magnetic force developed intermittently and 69 known as the interrupter-springs the so-called rotary-armature-finger 70 V which works in conjunction with the arma- ,84 and 85, and is ture of another electro-magnet known as the private-magnet; and a so-called rotary-arm 71. This lastarm has pivotally attached to its forward end a so-called rotary-pawl 72 which is subject to.the tension of a small coiled spring 73. One end of this spring is attached to the rearward and of the pawl, and the other to the rotary-arm 71. For the restoration of the switching'machine, a so-called releasemagnet is employed, which is usually composed of two. coils; but for the sake of simplicity and clearness only one coil 74 is shown. This release-magnet, like the rotary and vertical magnets, has placed before its pole-piece an armature 75 which is ivotally supported from the switch-frame By two pivot projections 76 and 77. Thisarmature, is normally held away from its pole-piece by a coiled spring 78, and has attached to it a flexible blade-spring 79 known as the release-link. This link lies horizontally under the release-magnet and passes between the verticalarm 54 and the L-shaped piece 55, already described. The forward end of this link is provided with an aperture 80 for normally holding the so-called double-dog 81, by its lug 82, against the pull of the doubledog-retracting-spring 83, when the switch is released. This double-dog is supported from the switch-frame by pivots rovided with two locking-arms 86 and 8% and with a third and downwardly-projecting arm 88, the ofiice of which latter will be disclosed later on. The private-magnet, to which reference has already been made, is composed of onlyone coil 90 Its armature 91 is supported from the private-magnet-frame (not shown), and works in a vibratory manner about a formed near its wardly-extending tooth-like projections 102 ward extremity bent downwardly at right angles thereto. This arm 94 carries certain mechanical details, as follows A lateral arm 96, designed to control the're'lation of three springs 97,98 and 99, known as the private-springs; a] tooth "escapement which includes two flexible springs 100 and 101, each of which springs is riveted by one end to the private-armature-arm one on the upper side and the cther on' the lower. The upper sprin is straight and has orward end two down- .and =-103;-but the underspr ng is bent at right angles, first downwardly and then at right angles againh'to jthe front. This double angle in this lower escapements I spring is'so. formed that said lower spring.

may.--cle'ar the bent portion 95 of the private-armature-arm 94, against which portion it.rests with a certain amountof tension, and so that there may be space to receive two other'tooth-shaped upwardlyprojecting pieces 104 and 105, which are formed on the forward. endof this escape- .ment-spring, and which are situated in juxtaposition to and slightly to the rear of the upper teeth. A retracting-spring 106, which has one end attached to the privatearmature normally holds said armature away from the private-magnet-pole-piece.

In conjunction with this escapement just described, there is a finger 108 at the right end extremity of a soecalled side-switcharm 109 normally Y retained behind the l-rearmost tooth of" the lower escapementspring. This. side-switch-arm has, near the base of the side-switch-fin or 108, a small forwardly-bent lug- 110. he arm 109 may be made to oscillate about the pivotal points 111' and 112, provided. near its middle,'and which have a common vertical axis. This side-switch-arm to the left of its center, carries a rearwardly-projecting member 113 to the extremity of which is pivotally secured a link 114. The other end of said link is bifurcated and engages the lower T-shaped extremity ofthe straight arm 88 on the double-dog 81. Very near the left extremity of the side-switch-arm there risesa shaft 115 which supports a number of wipers 116, 117, 118, 119 and 120,

any one of three positions, and each is nor mally in position to en ge' one of a series of contact-points, as f0 lows: 121, 122 and 123 124, 125,,and 12 127, 12s and 129; 130,

Ill

131 and 132; 133, 134 and 135. The sideparts, is known as the side-switch; and when the finger 108 that works in conjunction with the tooth escapement is in its rearmost position, the side-switch is said to be-in the first or normal position; when between the front and rear teeth, the sidesWitch is then said to be in the second position; and when said side-switch is in the third position the finger 108 is in front of or'outside of all of these teeth and rests against the so-called side-switch-stop 136. When in the first position, the wipers 116, 117, 118, 119 and 120 are respectively in contact with the contact-points 121, 124, 127, 130 and 133 in their order; but when in the second position, these wipers engage with contact-points 122, 125, 128,131 and 134, and in the third position with contactpoints 123, 126, 129, 132 and 135. The force that operates the side-switch in a forward direction resides in a retractingspring 137 fastened atone end to the switchframe, and at the other end to the sideswitch-arm One of the characteristic parts of the switch is a shaft 140 that has provided near its middle a set of circular or so-called 'vertical-ratchet-teeth 141 traversed by a vertical or longitudinal channel 142, into which there projects ,the extremity of a so-called shaft-rest 143'. Below the said circular or vertical-ratchet-teeth is located a set of longitudinal or so-called rotary-ratchetteeth 144 through the medium of which the shaft is given a step-by-step rotary motion. Just below these teeth thereis a cam-piece 145 which prevents the side-switch-arni from escaping too far when'it is shiftedfrom the first to the second position, as' will be more fully explained. Near the lower end of the shaft are supported the rotary and vertical line-wipers 146- and 147 which are insulated from each other and from the shaft. Just in front .of these wipers is the line-bank 148,. and just above them the private-wiper 149, in front of which latter is located the private-bank 150. There is a coil-spring 151 fastened near the upper end of the shaft with its outer extremity secured to a so-called guide or stop-pin 152. This spring retains said shaft in its normal position. Just below this spring there is an arm 153 known as the normal or stop-arm, which prevents the shaft from being rotated by said coiled spring beyond a certain point.v Said stop arm retains the channel along the circular, teeth, when the wipers are disengaged from the bank-contacts, in such a position that the shaft may be raised or lowered without any interference on the part of the shaftrest. Said normal-arm 153 also controls the position of a so=called normal-spring and 156 between which said normal-spring is situated; If electric pulsations are sent through the vertical-magnet 47, the vervtical-armature 50 is attracted-that is,'once each time the magnet is energized by apulsation or momentary closing of the circuit. At the first impulse or momentary closure of the circuit, and the consequent attraction of the vertical-armature, the vertical-pawl 0 .154 with respect to two', contact-points 155 switch-arm 109, with all its associated- 56 engages with one of the circular or socalled vertical-ratchet-teeth, thus raising the shaft one step, At the same time the.

vertical-arm 54 disengages the release-link 79 from the double-dog .81 by means of the L-shaped piece on said vertical-arm. As soon as the-double-dog 81 is released, the upper and lower locking-arms 86 and 87 fall against the circular and the 1011' tudinal-ratchet-teeth, respectively. T e upper locking-arm catches the shaft in its raised position and retains it there when the vertical-armature returns to its normal position after the vertical-magnet is de-energized. On the second impulse the shaft is raisedanother' step andagain caught a by the upper locking-arm, and 1s so actuated each. time the vertical-magnet is energized. If, immediately after the shaft is raised, the private-magnet 90 should be energized'once, the finger 108 on the sideswitch-arm will then disengage from the rearmost tooth of the lower escapementspring 101 upon the downward stroke of the armature91, and engage with the rearmost tooth of the upperescapement-spring Upon the return of said armature to itsnormal position, the finger 108 will disengage in turn from the upper rearmost tooth, permitting the side-switch to be drawn to the second position by the side-switch-retracting-spring 137. The lug 110 on the side-switch-arm then strikes the cam-piece 145 on the shaft and prevents a further advance of said side-switch, for the time be ing. After the side-switch is shifted to the second position, the step-by-step rotary motion of the shaft is. then brought about in a slightly different manner from the vertical motion. For instance:- When a circuit is. closed through the rotary-magnet 60, it includes the interrupter-springs 68 and 69. The rotary-armature- 63', upon'being attracted, causes the rotary-pawl to engage with one of the longitudinal-ratchet-teeth,

and the shaft is thereby rotated one step. In this advanced position the shaft is retained by thelower locking-arm 87 of the double-dog. Immediately after the shaft is locked, the interrupter-arm 67 separates the interrupter-springs, and the energizing circuit of the rotary-ma et is thus broken. It is evident that the rotary-armature 63 will then return to its normal posi tion under the tension of the rotary-armathe ture-retracting-spring 66. If the circuit through the rotary-magnet has not been broken atany other point, as soon as the interrupter-springs re-engage after the interrupter-finger is withdrawn from between them, the rotary-magnet will be re-energized, and the shaft will be rotated one more step, and so on until the circuit through the. rotary-magnet is broken permanently elsewhere.

When the shaft is rotated, the cam 145 is rotated with it out of the way of said lug 110, and the side-switch-finger 108 1s. then drawn against the front tooth 105 of the lower escapement-spring. If the privatemagnet is energized once more, momentarily, the side-switch-finger 108 wlll disengage from the lower front tooth and fall against the upper front tooth 103 at the downward stroke of the armature, and from the upper front tooth at the return of the armature to normal position; and the sideswitch-arm will be drawn to the third posi tion against the side-switch-stop 136. There are two other relays associated with a first-selector; one is known as the private-normal-relay 160, which has control through its armature 161 of a number of circuits that are connected with the so-called private-normal-relay-springs 162, 163 and 164; and the other the so-called bridge-cutoff-relay 165. By means of the armature 166 of the latter relay, 9. number of circuits are opened, and other desired objects are attained in connection with circuits that include a number of springs 167, 168, 169, 170, 171,172, 173 and 174. -The release mechanism of the first-selector is controlled through the release-magnet 74. If the switch has bee-n used, so that the shaft has been raised and rotated for instance, then when the release-magnet is energized the release-armature is attracted, and as a result the release-link 79 is brought forward far enough to cause the lug 82 of the double-dog 81 to engage the aperture in forward end of said link. Then when the releasemagnet is de-energized, the release-armature 75 is pulled back by the release-armature-retracting-spring 78. As a result, the doubledog-locking-arms 86 and 87 are drawn away from the circular and longitudinal ratchet-teeth on the shaft, and the side-switch is shifted to its first position by the double-dog-arm 88 and the intermediate link 114. The side-switcharm-finger 108, when pushed back, separates the escapement-springs 101 and 100 sufficiently to open a path of movement for itself, and is finallv caught behind the last lower tooth 104. When the vertical-magnet was energized for each step that the shaft was raised, the under surface of some circular ratchet-tooth was brought on a level with the upper surface of the shaft-rest 143,

and as soon as the shaft was rotated the cir-' cular tooth so raised rested and turned on the said shaft-rest. It is clear, then, that when the-switch has been raised and rotated, and if the double-dog is drawn away from the ratchet-teeth in a manner described, the

shaft will be left sub'ect to the tensionof the coil-spring 151. twill rotate then in 1 a backward direction upon the shaft-rest- 143, as before explained, until the stop-arm 153 strikes the, guide pin or normal- At this juncture, the shaft-rest a am enters f the channel 142, and the shaft y its own' All weight falls to its normal position.

are identifirst-selectors in the drawin cal in structure, so that the se ector shown at K, Figs. 3 and 6, has all its parts represented the same as the corresponding parts of the first-selector B, Fig. 1. Such parts are, for instance,.the-vertical line-rela 59 and the rotary-line-relay 107, the pmvatemagnet 138 and the release-magnet 139, the private-normal relay 157 with its armature '158, the vertical-magnet 58, the

' rotary-magnet 39, the private-normal-rechanical details of the connector repre-' sented at 0 Figs. 2, 5 and 6, are the same as those of the first-selector. For example,

the vertical-line-relay-magnet 200 and armature 201, the rotary-line-relay-m'agn 202 and armature 203, and the line-relaysprings 204, 205 and 206, the vertical-mag net 207, the vertical-armature 208, and

the vertical-arm 209. Said vertical-armv .is provided with the usual L-shaped piece 210 and the vertical-pawl 211. The armature 212 of the rotary-magnet 213 is, however, rendered conspicuous by the absence of the interrupter-finger and the rotaryarmature -finger 'found in the first-se'- lector.. The rotary-armature of the connector has only one' arm, and that is the rotary-arm 214' that carries the well-known 'rotary-ratchet-pawl 215.

The private-magnet 216, private-springs 217, 218, 219 and 220, and the .controlling arm 221, may-be clearly recognized. The escapement on the private-armature 222 differs slightly in that the upper escapementspring 223 has only one tooth 224; the lower spring 225. however, has the usual two teeth 226 and 227. The release-magnet 228 and the release mechanism is arranged differently. The release-armature 230 is situated on the right-hand side of the release-magnet, and is retained away from the release-magnet-pole-piece, by a simple retracting-spring 231. The release-link, instead of being mounted on the release-armature, is supported independently and permanently on some part of the switch structure. The double-dog performs the usual functions through its locking-arms 232 and 233 with regard to the shaft 234 and the circular and the longitudinal ratchet-teeth 235 and 236. The side-switch differs from the "first-salector-side-switch only in the fact that there are four side-switch-wipers 237, 238, 239 and 240 instead of five. The restoration of these wipers, and of the sideswitch-arm 241, is effected through the "side-switch-release-arm" 242 of the doubledog, as in the first-selector. The sideswitch-finger- 243 and the escapement of the private-ar'1nature work together in the manner described in connection with Fig.

- 4, excepfifllat the side-switch passes from the second to the third position against the side-switch-stop 244 at the downward instead of the return stroke of the privatearmature 222. The switch-shaft linewipers 246 and 247, the. line-bank 248, the private-wiper 249 and the privatebank 250 are the same as in the first-selector, as well as the cam 251 and the camstop 252 on the side-switch-arm. When the shaft is rotated, it is supported on the shaft-rest 253 by the circular ratchet-teeth; and said rotation is accomplished against the tension of the coiled spring 254, which latter is fastened to the shaft by itsinner end, and to the guide-pin 255 at its outer end. While the wipers are disengaged from the bank-contacts, the normal-arm 256 is held against the guide-pin or normal-post by the pull of the coiled spring, and in this way the shaft andall its parts are held in normal conditions. The release of the connector is brought about when the releasemagnet 228 attracts the release-armature 230. Said armature, when attracted, thrusts the double-dog 257 into engagement with the release-link and away from the ratchetteeth. The release-link falls over the lug 258 on the double-dog, retaining the latter in its new position. The shaft. being left free, is rotated in a backward direction on the shaft-rest by the tension of the coiled spring. As soon as the normal-arm strikes the guide-pin or normal post, the arm-rest enters the channel 259 along the circular teeth and leaves the shaft free to fall by its own weight to its normal position. It will be noticed that the release of the connector is accomplished as soon as the release-armature is attracted; but this differs from the release of the first-selector, which latter, it will be remmbered, releases only after the release-magnet is de-energized. The norma-l-spring 260 on the connector has only one contact-point 261 with which it ongages whenever the shaft is raised from its lowest or normal position. In addition, the

connector is provided with a so-called back-release-relay which is composed of two coils 262 and 263. Each of these coils has an armature indicated by the numbers 264 and 265, respectively. When these armatures are simultaneously attracted, the two springs 266 and 267 are closed, and thus employed to energize the release-magnet of the connector. Finally, there is a sigaling or ringer-relay 268 which, after a connect-ion is established, is energized when the calling subscriber presses the signaling-or ringing button. The armature 269 of this ringer-relay, when attracted, separates the called subscribers line from the calling subscribers line and places the former across the terminals of a ringer-generator D. This is done through the medium of a number of springs 270, 271, 272, 273, 274 and 275, which the ringer-relay-armature has under its control. The four sub-stations in Fig. 3, designated as Nos. 110, 210, 310 and 410, are each the same in make-up as sub-station A, Fig. 1, with the exception of the ringers or bells; for preferably the ringers or bells at the different stations are of different construction, or are differently combined with other lines, so that each responds only to its allotted character of current, or to only ringing current intended for it. In Fig. 2, the connectors represented by the letters E, G and I are the same as connector 0 and have similar parts similarly represented. These connectors use in common a busy signaling apparatus comprising a circuitinterrupter 276 and an induction-coil 277 with a primary winding 278 and a secondary winding 279; and having described the mechanical details and general operation of my system, the next step will be to describe its use in connection with the circuits.

In actual use, the operations are as follows: Assuming that the subscriber at sub station A (referring to Figs. 1, 2 and 3), wishes to establish connection with the subscriber at sub-station designated as No. 410, he (the calling subscriber) will first remove his receiver 8 from the switch-hook 9. As soon as the receiver is removed, the hook, rises, owing to the tension of a spring which is not shown, breaking contact as it rises with the so-called ringer-spring 280, and closing the talking-circuit-springs 17 and 18, the secondary circuit-springs 19 and 20, and the ground-springs 21 and 22. The closure of these last two springs places the so-called ground-post 33 in connection with ground-terminal G through the scriber presses the button 28 once.

springs 21 and 22 and conductor 281. The callin subscriber then proceeds by pressing t e push-button 27 four times. The spring 29, each time the button is pressed, breaks connection with contact-point 31 and closes with the ground-post 33. In this way, the vertical-line-conductor 34 is grounded four times in succession, thereby energizing the vertical-line-relay 40 of the first-selector B. The path of the enerizing current may be traced from round 5 at the sub-station A through springs 21 and 22, conductor 281, ground-post 33, spring 29, vertical-line-conductor 34, conductor 283, ,vertical-line-relay 40, lineswitching-relay-springs 173 and 174, conductor 284, conductor 285 to the nongrounded terminal of battery B and to ground G. Being energized, the verticalline-relay of the first-selector B attracts its armature 42 four times and grounds the spring 44 with the spring 45 four times in succession. The result is that the verticalmagnet 47 is energized four times, the current passing from ground Gr to springs 45 and 44, through conductor 286,privatesprings 98 and 97, conductor 287, sideswitch-wiper 117, conductor 288,-verticalmagnet-coils 48 and 49, conductors 289 and 285 to the non-grounded terminal of battery B and'to ound G. Each time the vertical-magnet is energized, the shaft is raised one step in a manner that has already been described; so that by four pulsations of the vertical-magnet, the shaft is raised four times, and the line and private wipers are thereby raised to the fourth level and placed opposite the first contact of the fourth row of their respective banks of contacts. At the first step, the normal-spring 154 separates from contact-point 155 and engages, instead, with the contact-point 156 which is connected with ground at G A guarding potential is, therefore, established at the connector private bank contacts corresponding to the number 500, which latter is supposed to be the number of the sub-station A; The path by which this guarding potential is transmitted may be. traced from ground Gr through lineswitching-relay-springs 167 and 168, con ductor 290, contact-point 156, normalspring 154, conductor 291, private-nor mal-springs 162 and 163 and conductor 408 which constitutes the private-normaltrunk-conductor that leads directly to the "connector-private-banks. It is evident that this guarding potential will remain on this line until the switch is released. Therefore, no subscriber may call this number until after he, the calling subscriber, is through. At the next step the calling sub- Spring 30 breaks from' contact-point 32 and comes in contact, momentarily, with the groundpost-33, The result now is that the rotary linerelay 41 at the first-selector B is energized once. The energizing circuit is from ground G at sub-station A to groundpost 33, through spring 30, rotary-lineconductor 35, conductor 292, rotary-linerelay 41, conductor 314, springs 172, 173 and .174, and conductors 284 and 285 to the non-grounded terminal of battery B and to is energized, the rotary-line-relay-armature 43 is attracted once, causing spring 46 to be grounded by coming in contact with spring 45. A circuit is thereby closed throu h the private-magnet 90, which may e traced from round G through springs 45 and 46', con uctor 293, privatemagnet 90, conductors 294, 295, 289 and 285 to the non-grounded terminal of battery B and to ground G. The private-magnet" is thus energized once, and its armature 91, by a downward and then a returned stroke to normal position, allows the side-switchfinger 108 to pass from behind the rearmost escapement-tooth 104 of the lower escapement-spring 101,.to the rear of the forward tooth of the same spring. The side-s witch-finge1" 108, however, does not quite strike the front tooth 105, but is prevented from doing this by the lug 110 on the side-switch-arm 109, which comes in contact with the cam 145. As soon as the side-switch is drawn to the second position, the side-switch-wiper 116 closes connection with contact 122, and a circuit 'is thereby closed through the rotary-magnet 60, energizing the same, and bringing about the rotation of the shaft.

The energizing circuit through the rotarry-magnet, beginning with ground G, extends through contact-point 122, sideswitch-wiper 116, conductor 296, interrupter-springs 69 and 68, rotary-magnet 60, conductors 295, 289 and 285 to the nongrounded terminal of battery B and to ground G. As soon as the rotary-armature 63 is attracted, the rotary-pawl 72 engages with the longitudinal teeth 144, and the shaft is rotated one step. The privatewiper 149 then engages with the first contact of the fourth row of the private-bank 150, and the line-wipers 147 and 146 engage respectively with the vertical. and the rotary contact-points of the first contactterminal of the fourth row of the linebank 148. As Soon as the shaft is rotated, the cam 145 disengages from the lug 110 on the side-switch-arm 109, and the sideswitch-armfinger 108 falls against the rear edge of the front tooth 105 of the lower escapement-spring 101, merely to rest there a short time. The rotary-armature-finger 70, being carried by the rotary-armature, depresses the private-magnet-armature 91, and immediately the side-switch-arm-finground G. When the rotary-line-relay 41- ger 108 disengages from the escapementtooth 105. As soon as said tooth is disengaged or cleared, the retracting-spring 137 draws the side-sWitch-arm forward, so that the finger 108 falls in turn against the rear of the upper front tooth 103. Immediately after the rotary-armature 63 strikes the "rotary-magnet-pole-piece", the interrupterfinger 67 is instrumental in opening the energizing circuit of the rotary-magnet at the interrupter-springs 68 and 69. As soon as the energizing current ceases to flow in said circuit, the rotary-armature-retracting spring 66 draws the rotary-armature back to its normal position. But, as the rotaryarmature-finger 7O begins to fall back, the private-magnet-armature 91 follows, and before the interrupter-springs 68 and 69 have had time'to re-engage, the side-switcharm-finger 108 clears the upper forward escapement-tooth 103, and the side-switch falls to the third position against the sideswitch-stop. 136. When the side-switch passes from the second to the third position, the side-switch-wiper 116 is then carried from engagement with the contact-point 122 into engagement with contact-point 123. By the time the interrupter-finger 67 permits the interrupter-springs to close contact, the circuit through the rotary-magnet is broken from ground at said side-switchwiper.. In the third position of the sideswitch, the vertical and rotary lineside-switch-wipers 119 and 120 are respectively engaged with the contact-points 132 and 135. It is evident that the line-conductors 34 and 35, at the end of the operation just described, are extended to the terminals of the line-bank 148, by way of the linewipers 146 and 147 and thence to an idle connector C (Fig. 2) that would be situated opposite the bank-contacts 0 by way of trunk-line-conductors similar to trunkconductors 297' and 298. Said connector has control of a ringer-generator that produces current of such frequency, for example, that only the bells of substation No. 410 will respond. It has been pointed out that connectors of the four-hundred or C- group, Fig. 2, fall under this type and draw ringing current from the generator D. A guarding potential is established at the first Contact of the fourth row of the privatebank 150 when the private-side-switchwiper 118 engages with the contact-point 129. This guarding potential exists by reason of a circuit which puts said private-contact-point in connection with the grounded terminal of the battery B through the ground Gr at the side-switch, contactpoint 129, private-side-switch-wiper 118, conductor 299, and private-wiper 149 to the private-contact-point with which it is engaged. Had the trunk-conductors leading from the first contact of the fourth row of the line-bank 148 been occupied by some other first-selector, the line-wipers 147 and 146 would not have been able to retain connection with said trunk-conductors. Had such been the ca.se-and not only the first contact of the fourth row, but also the next succeeding eight been occupiedthe first nine contacts of the fourth level of the private-bank 150 would have been supplied with a guarding potential. A guarding potential would have been provided at each individual private-contact-point in the same manner that was described in connection with the first contact-point. Under these conditions, if the calling subscriber energizes the private-magnet 90 once, by once pressing button 28, he causes the sideswitch to pass from the first to the second position; and'the rotary-magnet 60 will be energized the instant that the side-switchwiper 116 closes with contact-point 122. The shaft 140 is rotated one step by the rotary-pawl 72, and the wipers are switched into conjunction with the first contacts of the fourth levels of their respective banks. With the difference, however, that at the instant that the private-wiper' 149 closes with the first contact of the fourth level of the private-bank, a circuit is closed through the private-magnet 90. Battery current energizes said private-magnet in its passage from the grounded terminal G of battery B through an occupying switch and circuit not shown; through the first contact" of the fourth level of the private-bank, thence through the private-Wiper 149, conductor 299, private-wiper 118, contactpoint 128, conductor 300, private-magnet 90, and through conductors 294, 295, 289 and 285 to the non-grounded terminal of battery B The private-armature 91, is then retained by magnetic force against the private-magnet-pole-piece, and the sideswitch is detained in its second position with the side-switch finger 108 resting on the rear edge of the upper front escapementtooth 103. The energizing circuit through the rotary-magnet will be opened immediately after the rotary-armature strikes the rotary-magnet-pole-piece, as before, and the rotary-armature then returns to its normal position; but the private-armature does not follow as it did in the last case. The circuit through the rotary-magnet is closed again as soon as the interruptersprings re-engage; and the rotary-armature is attracted once, rotating the shaft to the second contacts; but the private-magnet still remains energized, owing to the guarding potential at the second privatecontact-point. Again the rotary-armature breaks the circuit through the rotarymagnet, and its armature returns to its normal position. These automatic operations are repeated as often as the private-Wiper 149 continues to encounter busy contactpoints. After the shaft is rotated nine steps,

and the private-wiper is enga ed with the ninth private-contact of the ourth level, the rotary-magnet is then energized once more, and the rotary pawl 72 rotates the shaft one more step; As soon'as the private-wiper leaves the ninth private-contact-point, the circuit through the privatemagnet 90 is then broken. The privatearmature '91 is then restored to the care ofthe rotary=armature-finger 70 which, at

this time, is drawn toward the private-mag- I net-pole piece. But, immediately after the shaft is locked with the wipers on the tenthcontacts,- the" circuit through the rotarythe non-grounded terminal of battery 13 magnet is opened, and the private-arma-' ture follows the rotary-armature to normal position. The side-switch then'passes to the third position, as in the first case, be-:

fore the interrupter-springs re-engage. The line-conductors 34 and 35 are now extended to a connector over the trunkJine-cOnductors 297 and 298 which lead from the tenth contact of the fourth level of thelinebank 148. This connector is represented at C Fig. 2. As soon as the private-sideswitch-wiper 118 closes with'the contactpoint- 129, a guarding potential is thereby established at the tenth private-contact of the fourth level so as to protect the'trunk line just occupied against intrusion, The

subscribers next operation is to press the. button 27 once, this act corresponding to the second digit of the number 410. The v'erti-- cal line-conductor 34 is thereby grounded at the ground-post 33, as it was in the first instance, with the result that the verticalliuerelay at the connector (3 is energized. The circuit, in this instance, passes from ground G to the v'ertical-line-conductor 34 through the vertical-side-switch wiper 119, contact-point 132, conductor 301 and vertical-line-wiper 147, verticaltrunk-conductor 297, vertical-line-relay 200, conductors 302, 303, 304 and 305 to the non-grounded terminal of battery B and to ground G. The armature 201 of the vertical-line-relay 200, upon being attracted,

closes a circuit through the vertical-magnet 207 from ground G. through springs,

205 and 206, conductor 306, privatesprings 218 and 217,'conductor1 307, side. switch-wiper 237, conductor 308, verti cal magnet 207 conductors 303, 304 and-305 to and to ground G. The vertical-magnet 207,1upon being energized but once this manner," raises the shaft234 one step by means of the-vertical-pawl 211, as was.

shown in connection with the first-selector? The wipers are thereby brought to a level with the first row of their respective banks,

just opposite the firstccontact terminals At the same time that the vertlcal-hne-relay magnet vwas ;first energized,

. ircuit through the normal-,cutsofi-relay 200 of the connector C is energized, the vertical-line-relay 40 of the first-selector Bis also energized; but the side-switchwiper 117 of said first-selector not being in contact with the first side-switch-connificance at this stage; The calling subscriber next presses the button '28 once and thereby energizes the ,rotary-line-relay 202 atthe connector C through a circuit as follows: from ground G of sub-station A to roundst 33, through Spring 30, rotaryfine-con uctor. 35, rptary-side-switch-wiper 120, contact-point 135, conductor 309.-

.tact-point 124, the energization of said ,first-selectorwertical-line-relay has no sigline-switching-relay-springs 171 and 170,

mg energized once, attracts its armatureonce, and the connector-side-switch" passes from the first to the second position in the same-manner. thatthe first-selector-side switch did when the first-selector-privateswitch arm-fin er 243 at; the downward stroke of the private-armature 222 leaves .the lower escapement-tooth-- 226 and is caught by the escapeInent-tooth 224 just above; and on the returned stroke of the said. private-armature the side-switcharm passes to a position behind the front lower escapement-tooth' 227. ground impulse or'momentary closure of the circuit that operates the rotary-line-relay 202 of the connector 0 also energizes the: rotary-line-relay 4110f the first-5e leotor B, as well as the norrnal-cut-ofirelay 160. But-the operations'ofthese last two relays of the;fir'st-selector-B are of no efiect, at present. The energizing circuit through the rotar dine-relay ready been points out. Theenergizin 1s as follows: from ground G at substation A over the rotary-trunk-conductor The sidelhe same conductor 310 rota -line'-wi er 146 roa Q P a 35 throu .h the -rotary-sideswitch-wiper 120, con uctor 309, springs 171 and- 170,

conductor 313,- private-normal-relay 160,

conductor314, springsl 172, 173 and 174,

conductors 284 and 285 to the non-groundedterminal of 'battery B ".and to ground vG. At the-next operation, the calli subscriber presses button 27 ten times, this switching operation correspondin to the last digit of the number to be ca ed. The verticalline-conductor 34 being grounded ten times, the verticaLline-relay 200 of the connector C operates its armature 201 ten times. The energizing circuit throu h this relay has already been traced.- The vertical-linerelay-armature 201, in bringing the springs 205 and 206 together, closes a circuit through the rotary-magnet 213 each time. This circuit begins at ground G and extends through line-relay-springs 205 and 206, conductor 306, privatesprings 218 and 217 conductor 307, side-switch-Wiper 237 conductor315, rotary-magnet 213, and conductors 304 and 305 to the non-grounded terminal of battery B and to ground G. Each time the rotary-magnet is ener mod the rotary-armature 212 is attracte and the shaft is rotated one ste so that the subscriber, by ressing the utton 27 ten times, rotates t e shaft 234 ten ste s or places. At the tenth step, the private and line wipers will be found in contact with the tenth contact-terminal of the first level of their respective banks. The line- Wipers 246 and 247 are 'then in connection with the line of subscriber No. 410, which latter terminates at the tenth terminal of the first level of the line-bank 248. But as the side-switch is still in the second position, thecalling subscriber is not yet in direct connection with the desired line. It is necessary for 'the side-switch-wipers 239 and 240 to pass from their second position to the third position into connection with contact-points 317 and 316, respectively, at which time the circuit will be completed over the conductors 318 and 319 which connect said points with the linewipers. In the next operation, the calling subscriber presses the button 28 once and for the last time. The rotary-line-conductor 35 is now grounded once, and the rotaryline-relay 202' at the connector C attracts its armature once. The private magnet 216 is again energized once, and its armature 222 is attracted. The front tooth 227 on the lower escapement-spring then clears or disengages the side-switch-armfinger 243, at which instant the sideswitch springs into its third position before the private-armature returns to its normal position. After the connection is completed, thesignaling-button 23 at sub-station A is pressed. The vertical-line-relay 200, at the connector C is thereby ener ized by a current passing from ground 1 at sub-station A through springs21 and 22, contact-point 26, spring 24, thence through springs 19 and 20, contact-point 3,1, vertical-line-relay 200 to the non-grounded terminal cf battery B and to ground G. When the vertical-line-rela is thus energized at this time, and the inereIay-springs 205 and 206. are brought into contact, the ringer- 268, conductors 332, 333, 334, 335, 302, 303,

304 and 305 to the non-grounded terminal of batteryB and to ground G. When the ringer-relay is energized, the ringer-springs 271 and 274, which constitute the terminals of the called subscribers line, are closed respectively With the ringer-relay-springs 272 and 275. An alternatlng. current is then projected on the normal-trunk-conductors 329 and 330 and thence to the line-conductors across which is located the sub-station desired in this case sub-station No. 410. This alternating current is, for example, of such a nature that, although it passes through all the ringers that are bridged across the line-conductors 199 and 282, only the ringer 336 at sub-station No. 410 re sponds. The path of the ringing current through the hell or ringer 336 is from generator D through ringer-relay-springs 275 and 274, side-switch-Wiper 240, contactpoint 316, conductor 319, rotary-linewiper 246, rotary-trunk-conductor 330, rotary-line-conductor 282, spring 337, contact-point 338, conductor 339, condenser 340, ringer 336, ringer-spring 341, switchhook 342, conductor 343, contact-point 344, spring 345, vertical-line-conductor 199, vertical-normal-conduc-tor 329, verticalline-wiper 247, conductor 318, contactpoint 317, side-switch-wiper 239, and ringer-relay-springs 271 and 272 to generator D. The subscriber at sub-station No. 410, upon hearing the bell ring, will remove the receiver from its hook, thus breaking the ringing circuit between the hook 342 and the spring 341 and closing contact between the secondary springs 346 and 347, and between the local springs 348 and 349 and the ground-springs 350 and 351. The calling subscriber, upon releasing the signaling-button, restores the vertical-linerelay 200 and the ringer-relay 268 of the connector C, so that the circuit from sub-station No. 500 to substation No. 410 is completed from the receiver 8 through conductor 352, secondary winding 16 of induction-coil 12, contact-point 25, spring 24, thence to springs 19 and 20, contact-point 31, spring 29, vertical-line-conduotor 34, side-switch-wiper 119 of the first-selector B, contact-point 132, conductor 301, vertical line-wiper 147, trunk-conductor 297, condenser 354 of connector 0 conductor 355, ringer-relay-springs 270 and 271, side-switch-wiper 239', contact-point 317, conductor 318, vertical-wiper 247, normal-conductor 329, line-conductor 199, spring 345, contact-point 344, conductor 343,

I secondar springs 346 and 347, conductor 356, pus -button.spring 357, contact-point 358, seconda winding 359 of 1nduct1oncoil 360, con uctor 361, receiver 362,

point 316, side-switch-wiper- 240, springs l 274 and 273, conductor 364, condenser 365, trunk-conductor 298, rotary-line-wiperi 146 of the first-selector B, conductor 310,

to ground, the vertical line-reley 40 is en ergized, and the spring 44 is brought into engagement with'the grounded springet, so that the three line relay-sprmgs are closed simultaneously.

As soon as the spring 44 touches the spring 45, the release-magnet 74 of the firfSt-selector is energized throu h the following circuit: from round through springs 45. and 44, con uctor 286', privatesprings 98 -and=99, conductor 369, rolease-magnet 74, conductors 295, 289 and line-switching-relay-springs 170 and 171,\285 to the non-grounded terminal of batconductor 309, contact-point 135, sideswitch-wiper 120, rotary-line-conductor .35, spring 30, contact-point 32, conductor 366, and back to receiver 8. The two subscribers are now ready to converse, and when the subscriber at sub-station No. 410 speaks in the transmitter 367 in a manner wellknown, and through the means of a battery 368 and the induction-coil 360, the electric pulsations corresponding to the sound waves that are received in the transmitter are induced or repeated into the secondary winding 359 of the induction-coil. This induction-coil has been describedv in the circuit I at that station.

with the receiver 8 at sub-station A, so that when the subscriber at sub-station No. 410 talks into his transmitter, the subscriber at sub-station A is able to hear what is said Similarly, when the subscriber at sub-station A talks into his transmitter 11, electric pulsations are induced in the secondary'winding 16 of the inductioncoil 12; and said coil being in series with the receiver 362 at sub-station No. 410, the called subscriber is able to hear the conversation from said sub-station A. When the conversation is over, the switches may all be released by the calling subscriber, if hev presses the buttons 27; and 28 simultaneously. The rotary. and vertical lineconductors 35 and 34 are then grounded at zation of the rotary-line-relay causes the private-magnet to attract its armature, as in other cases, separating the privatesprings 2 17 and 218, and causing the latter to engage with the private-spring 219, as well as with private-spring 220with the last one incidentally. Now, as soon as the "vertical-line-cbnductor 34 is connected tery B and toy ground G. The releasearmature 75 is then attracted, and the release-link 79 is so shifted that the aperture 80 in its forward end falls over the lug 82 of" the double-dog and remains "in that position as long as the springs 29 and 30 at sub-station A are kept on the ground-spring 33. At the same time, the vertical-linerelay at the connector (1 is energized, causing the line-relay-springs 206 and 205 to close in contact and to be retained so, together with the third line-relay-spring 204, as long as both line-conductors are kept grounded. At the instant that the springs 205 and 206 at the connector come into contact, the release-magnet 228 is energized throu h a circuit as follows: from ground Gr t rough springs 205 and 206, conductor 306, private-s rings 218 and219, conductors 370 and 3 1, release magnet-228, conductors 302, 303, 304 and 305 to the non-groundedterminal of batter B and to ound G. As soon as the re ease-magnet attracts its armature 280,- the locking-arms 232 and 233 of the doubledog 257 are drawn away from the ratchetteeth on the shaft. The shaft, bein leftto the tension of the coil-spring 2 4, rotates in a backward direction upon the shaft-rest 253 until the normal-arm 256 meets the guide or normal-post 255. At that instant, the wipers clear the bank-terminals, the shaft-rest enters the channel 259 that traverses the circular ratchet-teeth, and the shaft of its own weight drops to its normal position. At the same time that the locking-arms are drawn away from the shaft-ratchet-teeth, the side-switch-releasing-arm 242 on the double-do through the medium of the side-switch-link 372, rotates the side-switch about its pivots to the first position, locking the side-switcharm-finger 243 behind the rearmost lower escapement-tooth of the escapement-spring 225. As soon as the side-switch-wiper 238 moves from engagement with the contact-point 373, the circuit through the private-wiper to ground is broken, and the guarding potential is removed from the tenth contact of the first level of the pri vate-bank. Therefore, the line-switchingw relay of the first-selector K is also re- 

